Cementing plug



Sept. 28, 1943. c. E. BURT 2,330,266

I CEMENTING PLUG Filed March 16, 1942 f0 K 13 23 I CZAEE/VCE 51' 5025 INVENTOR.

(9W ATTORNEY Patented Sept. 28, 1943 units CENEENTING PLUG Clarence E. Burt, Los Angeles, Calif., assignor to Baker Oil Tools, 1110., Vernon, Calif., a, corpora.-

tion of California Application March 16, 1942, Serial No. 434,894

2 Claims.

The present invention relates to cementin plugs capable of separating charges of cement slurry and other fluids employed in the cementing of casing in well bores.

Cementing plugs must be placed in proper upright position when introduced in a well casing to perform their function of separating charges of cement slurry and mud or other fluids, and thus prevent their commingling and contamination of the slurry. If the plug were inserted in the casing in inverted position, such contamination might occur. In the case of a bottom cement plug employed at the bottom end of a charge of cement slurry, it might be impossible to eject the slurry from the well casing upon engagement of the bottom'cementing plug with the internal parts of a well shoe or collar.

Accordingly, it is an object of the present invention to provide an improved cementing plug which cannot be intentionally or inadvertently inserted in a well casing in inverted position.

In its general aspects, the invention contemplates a cementing plug having a packing member adapted to slidably engage the wall of a well cementing plug in the casing in inverted position. However, when the plug is in an upright or proper position, these restraining or preventing elements cannot preclude introduction of the plug in the casing, norits subsequent downward movement with its packing member in slidable sealing engagement with the wall of the casing.

This invention has other objects which will become apparent from a consideration of the device shown in the drawing accompanying and forming part of the present specification. This device will now be described in detail to illustrate the general principles of the invention, but it is to be understood that such detailed description is not to be taken in a limited sense, since the scope of the invention is best defined by the claims appended hereto.

Referring to the drawing:

Figure 1 is a. side elevation of a cementing plug embodying the present invention;

Figure 2 is a cross-section taken along the line 2-2 in Figure 1;

Figure 3 is a longitudinal view illustrating an attempt to introduce the plug in a well casing in inverted position; and

Figure 4 is a longitudinal view of the plug in proper position Within a well casing.

The specific cementing plug A disclosed in the drawing is designed for operation as a bottom plug. That is, it is placed in the casing 13 at the lower end of a charge of cement slurry, to prevent contamination between it and the preceding charge of mud or other fluid employed in the well. It is to be understood, however, that the inventionis also capable of use in connection with top or other cementing plugs.

The cementing plug includes a body l0 made of any suitable material, such as synthetic resin, rubber, wood, aluminum, magnesium, etc. This body consists of upper and lower portions H, H whose ends l3, l4 are generally cylindrical, and an intermediate portion l5 of reduced diameter. The upper and lower portions of the body taper inwardly toward each other from their cylindrical surfaces to the intermediate portion.

A packing member or disc I6 of rubber or other flexible material is suitably secured to the body at its intermediate portion I5, as by molding, casting or clamping it therein. This packing member is designed to slidably seal with the wall of the well casing B as the plug moves within it, but it is also capable of flexing downwardly upon arresting of the plug body ill to permit downward by-passing of cement slurry or other fluids around the plug. Such downward flexing of the packing member i6 is allowed by the reduced intermediate portion E5 of the body and the tapered lower surface 12a. Similarly, the packing member may flex upwardly due to the tapered surface lid of the upper body portion extending from the intermediate portion IS. The generally cylindrical ends l3, M of the body serve to prevent substantial tilting of the plug as it moves through the casing.

It is to be noticed that the lower part l2 of the plug body is provided with by-pass openings l1 extending inwardly from its periphery to the plug axis. However, the upper section H of the body does notcontain such openings. These bypass openings permit the cement slurry to pass downwardly beyond the flexible packing member l6 and through the openings l'l into and through a casing collar or shoe capable of arresting downward passage of the cementing plug A within the casing.

As the cement slurry is pumped down the casing B with the bottom plug A at its lower end, the flexible packing member l6 probably is deflected slightly in an upward direction and moves downwardly in sealing engagement with the wall of the casing under the influence of the cement slurry above it and the pumps at the surface of the well bore. tion It of a cement collar, shoe, or other barrier C in the well casing, the body iii of the bottomplug can no longer move downwardly, which enables the cement slurry above the plug to deflect the packing member l6 downwardly and inwardly, as permitted by the relieved body portion In, and pus into the by-pass openings I; at the lower-end of the plug, from where it may flow through the shoe or collar passage is for election from the well casing, in a known manner (see Figure 4) i If the bottom cementing plug were to be inserted in the well casing in inverted position, the fiat top surface it at the normally upper end'of the plug body would engage the fiat upper end of the internal portion it of the shoe or collar and prevent lay-passing of the cement slurry around the plug A for passage through the collar C and subsequent ejection from the casing B. The end 2| of the upper plug body portion would make an effective seal with the top of the collar or shoe portion l8 and preclude such passage of cement slurry around the plug. As a result, it would be necessary to pull the entire string of easing from the well bore to eliminate the charge of slurry in the well casing, or, whenever this could not be done, it would become necessary to drill out the cement in the casing and begin the cementing operation .over again with the cement plug properly placed in the casing.

In order to avoid the above hazard, it is proposed to incorporate elements in the plug which preclude its insertion in the casing in inverted position, but which do not prevent its proper functioning when inserted in upright position in the casing. In the example shown in the drawing. such elements consist of leaf springs 22 that are molded or otherwise secured to-the plug body and have circumferentially spaced fingers 23 extending laterally outwardly and upwardly to a material extent beyond the periphery of the flexible packing member it. These fingers are disclosed in the drawing as extending outwardly and upwardly from a point adjacent the flexible packing member IE, but it is to be understood that they can be disposed in any other suitable position on the plug body Iii.

Should an attempt be made to place the plug in the casing in inverted position, the outwardly extending spring fingers 23 would engage the top 26 of the casing and preclude such introduction (see Figure 3). The resistance to introduction would immediately apprise the operator of the fact that the plug was in the wrong operative position.v Upon disposing it in proper upright position, the plug A passes readily into the easing B, since the upwardly extending spring fingers 23 can be deflected inwardly toward the plug body with the exertion of comparatively little force, as permitted by the reduced tapered body portion HG.

Once the plug is inserted properly in the well casing, the spring fingers 23 merely ride alon Upon striking the internal porthe wall of the casing and do not interfere with the ordinary functioning of the plug. As seen in Figure 4, the spring fingers 28 are deflected upwardly and slide along the casing wail without ofiering much resistance to downward passage of the plug. These spring fingers do not inter,- fere with the slight upward deflection of the packing member l6 as the plug is being moved down through the casing, and also they 'have no eil'ect whatsoever upon the downward deflection of the packing member upon engagement of the plug body ill with the shoe or collar 0, to permit by-passlng of the cement slurry through the bottom plug by-pass openings H for ejection from the casing,

It is therefore apparent that a cementing plug has been disclosed which cannot be inserted in a well casing in inverted position. but which can function in its normal intended manner when properly placed in the casing.

I claim:

1. A well cementing plug adapted for use at the bottom end of a charge of cement slurry, including a body having a generally cylindrical im erforate upper portion to prevent flow of liquid therethrough and a lower portion provided with by-pass openings to permit flow of fluid around said plug, said upper and lower portions tapering inwardly toward each other to provide an intermediate portion of reduced diameter, a packing disc secured to said body at said intermediate portion and adapted to slidably seal with the wall of a well casing, and flexible spring fingers secured to said body adjacent and above said packing disc and extending upwardly and radially outward therefrom a material distance beyond the periphery of said packing disc, said flexible spring fingers being deflectable inwardly and away from said packing disc by said casing to permit upright insertion of said plug in said casing, and defiectable outwardly and adjacent said packing disc by the end of said casing if inverted insertion of said plug therewithin is attempted.

2. A well cementing plug adapted for use at the bottom end of a charge of cement slurry, including a body having upper and lower portions, packing means secured to said body for slidable sealing with the wall of a well casing, said upper body portion being imperforate to prevent flow of fluid therethrough and said lower body portion having by-pass openings to permit flow of fluid around said packing means and body, and flexible spring fingers secured to said body adjacent and above said packing means and extending upwardly and radially outwardly therefrom a material distance beyond the periphery of said packing means. said flexible spring fingers being deflectable inwardly and away from said packing means by said casing to permit upright insertion of said plug therewithin and defiectable outwardly and against said packing means by the end of said casing if inverted insertion of said plug therewithin is attempted.

CLARENCE E. BURT. 

